Chiral auxiliaries have been extensively used in asymmetric syntheses. Traditionally, N-acyl 2-oxazolidinones have been synthesized by lithiating the oxazolidinone with n-butyl lithium at -78.degree. C., followed by acylating with an acyl chloride. N-acyl sultams have similarly been synthesized by deprotonation with NaH, followed by N-acylation with an acyl chloride. Such two step procedures have been used to convert the oxazolidinone or sultam to the respective trimethylsilyl derivatives, followed by reaction with excess acyl chloride in refluxing toluene. Neither of these synthesis schemes is particularly useful when the acyl side chain contains substituent groups that are reactive. Also, these reactions take an inordinately long time to run to completion. The present invention overcomes the disadvantages in these processes.
When deptotonation is effected with a strong base, followed by acylation using an acid chloride or anhydride, side reactions frequently occur if the substrate contains other functional groups.
Copending application Ser. No. 281,394, filed on Jul. 27, 1994 addresses the N-acylation of oxazolidinones and 2,10-sultams. The present application addresses the N-acylation of other ring systems.